Wear indicating device for drill bits



Jan- 15 1952 D. l.. DEL HOMME WEAR INDICATING DEVICE FOR DRILL BITS Filed Sept. 22, 1949 smigi" Hoffi/Y2@ INVENTOR. 'Mmm A TTORA/EYS Patented Jan. 15, 1952 WEAR INDICATING DEVICE FOR DRILL BITS Daniel L'. DelHomme, Houston, Tex., assi'gnor to Reed Roller Bit Company, Houston, Tex., a corporation of Texas Application September 22, 1949, Serial No. 117,128

6 Claims. (Cl. Z55-61) This invention relates to new and useful improvements in wear indicating devices `for drii bits. f v

In well drilling, maximum efficiency is obtained when `the drill bit which is attached to the lower end'of the-drill pipe is used until it is substantially dull and is no longer capable of performing the drilling operation. It has heretofore been the practice to rely solely upon the` driller and hisparticular knowledge based upon experience Withrespect to ythe time when the drill bit has dulled and shouldbe removed, and obviously the human element of error has always been present withthe result that in many instances the bit has 4been pulled or removed from the well prematurely or too long after the drilling bit has lost its eiliciency.

It one object of the present invention to provide an improved indicating device which will automatically signal to the surface when the drill bit is worn to a predetermined point whereby aca curate information as to the condition of the drill bit is made known to the driller or operator.

An importantobjectof the invention is to provide a wear indicating device for drill bits wherein the pressure of the ldrilling fluid is utilized as a signalling medium and also wherein aY sudden variation in said pressure is indicativeof the fact that the bit yhas been worn to a predetermined point.

A further object is to provide a device, of the character described, wherein a fluid discharge opening is normally sealed vby a movable valve element, together with means actuated when the drill bit wears to a predetermined point for permitting the valve member to open the discharge port and thereby cause a pressure variation in the? circulating iiuid which will function to signal the opening of said port and the wear of the bit to the surface.

Still' another object is to provide an improved indicating device which may be readily applied toa drill bit of ordinary construction and which includes. a piston-like valve member normally closing a discharge Outlet, together with liquid means for maintaining the piston valve in a position closingy saidoutlet; wear of the bit to a predetermined point releasing the liquid means to allow movement of the piston valve and opening of the discharge outlet.

Other and further objects of the invention will appear from the description of the invention.

51u .the-acompanying drawings, which form a partfof the instant specification, which .are to be read in conjunction therewith, andvwherein 2 l like reference numerals are used to indicate like parts in the various views:

Figure l is an elevation of the drill bit having the improved indicating device constructed in accordance with the invention mounted thereon,

Figure 2 is a bottom view of the drill bit,

Figure 3 is an enlarged longitudinal sectional view taken through the indicating device and illustrating the piston valve in a position closing the discharge outlet, and

Figure 4 is a View similar to Figure 3 with the piston valve in a position opening said outlet.`

In the drawings the numeral I@ designates a bit body which has the usual threaded box II at its upper end whereby the bit may be connected to the lower end of a drill pipe or stem A. The usual fluid cavity or chamber I2 is formed in the bit body and cutting blades I3 are welded or otherwise secured to the lower portion of said body. Drilling fluid circulating passages i4 extend from the cavity I2 and discharge from the lower portion of the body adjacent the blades I3 (Figure 2). As illustrated the blades I3 are d isposed transversely of the bit body and have their lower cutting edges I3a located in a plane below the lower end of the body. When the cutting blades have been worn through the drilling operation to approximately Ythe line indicated at B in Figure 1 or their vertical or reaming edges have been worn to the line indicated at C in this figure, it is desirable that the bit be replaced for at such time the bit is completely dulled.

For indicating that the bit blades I3 are worn either to the point B or the point C the improved indicating device D is arranged to be mounted on the bit body. As isclearly shown in Figures 3 and 4, the vdevice includes a tubular cylinder I5 having an axial bore I6 extending entirely therethrough. The upper end of the cylinder is threaded into van elbow I'I Land communicates with the bore I8 of said elbow. The lateral leg of .the elbow Il is arranged to be threaded within an opening I-9 which is formed in the wall of the bit body and which communicates with the iiuid cavity or chamber I2. of the bit. The cylinder I5 has a plurality of discharge openings or outlets 20 provided in its upper portion and said outlets establish communication between the bore of the cylinder and the Well bore E within which the bit is disposed.

For controlling the flow of drilling uid which is normally circulated downwardly through the drill pipe A and into the chamber of the bit outwardly through the elbow Il and outlets 2D, a cylindrical valve member 2I is slidable within the bore I6 of the cylinder I5. A sealing ring 22 is mounted at each end of the valve member 2l and seals with the bore I5 of the cylinder. When the valve member is in its raised position as shown in Figure 3, said member functions to close the outlet ports 20 and thus the drilling fluid circulating through the chamber or cavity I2 of the bit body cannot escape outwardly through said outlets; however, when the valve member 2 I is moved downwardly as shown in Figure 4 the drilling fluid from within the cavity I2 may pass outwardly through the elbow Il into the upper portion of the cylinder I5 and then outwardly through the openings or outlets 2i) in the wall of said cylinder. The cross-sectional area of the discharge openings or outlets 2B are at least equal to the bore of the connecting elbow I'I which is in itself relatively large, whereby when the valve is moved downwardly as shown in Figure 4, a very noticeable pressure drop will occur in the pressure of the circulating iiuld. f

For locking the valve member 2i in its raised position until such time as the bit blades I3 are worn to either of the dotted lines B or C, the lower portion of the cylinder is adapted to receive a liquid medium. This liquid is retained within the lower portion of the cylinder and also within a wear tube 23 which has its lower end closed and its upper 'end threaded into a coupling collar 24 which collar is threaded onto and closes the lower end of the cylinder. The liquid is adapted to be introduced into the cylinder below the valve member and into the wear tube through a back check valve 25 which is mounted in the lower portion of the wall of the cylinder I5. It is evident that when liquid is introduced through the check valve 25 such liquid will drive the valve member 2i to its upermost position against an abutting shoulder' Ila formed within the connecting elbow and said liquid will entirely lill the lower portion of the cylinder and the interior o the wear tube 23. It is evident that said liquid will thereby lock the valve against downward movement within the cylinder.

The wear tube ze is located Contiguous to the subcombinations.

outer surface of the bit body and extends to a desired point with respect to the bit blades I3. As shown in Figure l, the closed end of the wear tube is located at substantially the point of intersection between the dotted lines B and C which are the points of wear of the bit blades at which a signal is desirable.

In the operation of the device, the indicator unit D is mounted on the external surface ofthe bit body and a. suitable liquid is introduced through the check valve 25 to move the valve member 2I to its uppermost position and to thereby lock the same against downward movement within its cylinder. In such position the valve member 2l closes the discharge outlets 20 in the wall of the cylinder. With the valve member closing the discharge outlets 20 the bit is lowered in the usual manner into position and the` drilling operation proceeds.

As the bit is worn either to the point B or to the point C in Figure 1, the abrading action of the formation against the lower end of the wear tube 23 results in a wearing away of said closed end, whereby the wear tube is opened and the liquid which normally locks the valve member 2| in its upper position is released. The drillingl fluid is, of course, being constantly circulated downwardly through the drill stem and chamber I2 and is normally discharged throughthe passages I against the bit blades, and this drilling fluid is, of course, under a predetermined or known pressure. As soon as the wear tube 23 has its end worn away and the liquid locking the member in its raised position is released, the valve member is caused to move downwardly by the pressure of the circulating drilling fluid which is constantly acting against its upper end through the connecting elbow I'I. As the valve member is moved downwardly to the position shown in Figure 4 the discharge outlets 20 are uncovered and thus, the circulating drilling fluid may escape through said outlets. Because the size of the outlets is substantial the sudden -opening of the outlets 20 results in a sudden or abrupt pressure drop in the pressure of the circulating drilling fluid and this pressure vdrop is an immediate indication to the operator that the wear tube 23 has been opened which means that the bit blades I3 have worn to a predetermined point. Thus an indication is provided at the surface that said bit requires replacement,

It is pointed out that the Wear tube 23 is closely confined against the external surface of the bit body and extends contiguous to the rear surface of one of the blades I3 so that under normal drilling it is protected against undue wear and premature abrasion which would release the liquid. The invention is shown as applied to the usual blade type drill 1bit but it is apparent that said bit may readily be employed with any of the ordinary bits now in general use. It is also noted that the end of the wear tube may be located in any desired plane so that the signal is given when the bit wears to a predetermined p-oint.

From the .foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the structure.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made;

of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

Having described the invention, I claim:

l. In combination, a drill bit having cutting elements thereon and also having an opening in its wall, means for circulating a pressure drilling fluid through said bit, a movable valve having one end exposed to the pressureof the drillingY fluid and movable relative to the openingrfor con.

trolling flow through said opening, a closed chamber having a liquid therein and having the.

opposite end of Said Valve exposed to-said. liquid,

whereby said liquid functions to lock said valve against movement and in a position closing theY opening, and means normally closing the chamber and adapted when opened to release the liquid from the chamber, the chamber closing means comprising a wear element on the exterior of the body which is located to be contacted by the formation when the cutting elements of the bit are worn down to a predeterminedv point, whereby the fluid: in the chamber may escape and the circulating drilling fluid may move the valve to an open position to permit said circulating uid to discharge through the opening to 5 thereby vary the pressure of the drilling uid Within the bit.

2. In combination, a drill bit having cutting elements thereon and also having an opening in its Wall, means for circulating a pressure vdrilling uid through said abit, a movable valve having one end exposed to the pressure of the drilling uid for controlling iiow through said opening, a closed chamber having a liquid therein and having the opposite end of said valve eX- posed to said liquid, whereby said liquid functions to lock said valve against movement and ina position closing the opening, a wear tube extending from the liquid chamber and having its outer end closed and located exteriorly of the bit adjacent one of the bit blades, said outer end being adapted to be abraded away when the cutter elements of the bit have worn to a predetermined point during a drilling operation to release the liquid from the chamber and thereby permit' movement of the valve to an open position allowing flow of drilling iiuid through the opening in the bit.

3. The combination with a drill bit having cutter elements and having an opening in its wall, of a wear indicating assembly including, a cylinder having one end communicating with the opening in the bit and its opposite end closed, said cylinder having a discharge outlet in its wall intermediate its end, a valve slidable in the cylinder and movable to positions closing or establishing flow from the opening in the bit to the discharge outlet in said cylinder, means for introducing a liquid into the cylinder between the valve and the closed end of the cylinder to move the valve in a position shutting off ow to the discharge outlet and to normally lock the valve against movement from such position, and means mounted in the wall of the cylinder and disposed exteriorly of the bit body for opening the closed end of the cylinder when the cutting elements have Worn to a predetermined point during a drilling operation to release the locking liquid and allow the valve to move within the cylinder and thereby establish communication between 5. The combination as set forth in claim 3,

wherein the means for opening the closed end of the cylinder comprises a wear tube communicating with the cylinder and extending therefrom, the free end of said tube being normally closed to conne the locking liquid and being adapted to be abraded away by the formation within which the drill bit is performing a drilling operation, said wear tube extending contiguous to the outer surface of the bit body and having its closed end terminating in a predetermined plane with respect to the cutting elements of the bit, whereby said tube is opened when said cutter elements have worn to a predetermined point.

6. The combination as set forth in claim 3, wherein the means for introducing the liquid Within the cylinder is a back check valve mounted in the wall of the cylinder.

DANIEL L. DELHOMME.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,461,164 Lewis Feb. 8, 1949 2,489,687 Thrift et al Nov. 29, 1949 

